From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AB1EBC433E0 for ; Tue, 19 Jan 2021 21:10:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 69E7F22D08 for ; Tue, 19 Jan 2021 21:10:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387746AbhASStF (ORCPT ); Tue, 19 Jan 2021 13:49:05 -0500 Received: from verein.lst.de ([213.95.11.211]:52920 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390680AbhASSBJ (ORCPT ); Tue, 19 Jan 2021 13:01:09 -0500 Received: by verein.lst.de (Postfix, from userid 2407) id 8D84068B02; Tue, 19 Jan 2021 19:00:24 +0100 (CET) Date: Tue, 19 Jan 2021 19:00:24 +0100 From: Christoph Hellwig To: Marc Orr Cc: kbusch@kernel.org, axboe@fb.com, hch@lst.de, sagi@grimberg.me, jxgao@google.com, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] nvme: fix handling mapping failure Message-ID: <20210119180024.GA28024@lst.de> References: <20210119175336.4016923-1-marcorr@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210119175336.4016923-1-marcorr@google.com> User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Tue, Jan 19, 2021 at 09:53:36AM -0800, Marc Orr wrote: > This patch ensures that when `nvme_map_data()` fails to map the > addresses in a scatter/gather list: > > * The addresses are not incorrectly unmapped. The underlying > scatter/gather code unmaps the addresses after detecting a failure. > Thus, unmapping them again in the driver is a bug. > * The DMA pool allocations are not deallocated when they were never > allocated. > > The bug that motivated this patch was the following sequence, which > occurred within the NVMe driver, with the kernel flag `swiotlb=force`. > > * NVMe driver calls dma_direct_map_sg() > * dma_direct_map_sg() fails part way through the scatter gather/list > * dma_direct_map_sg() calls dma_direct_unmap_sg() to unmap any entries > succeeded. > * NVMe driver calls dma_direct_unmap_sg(), redundantly, leading to a > double unmap, which is a bug. > > Before this patch, I observed intermittent application- and VM-level > failures when running a benchmark, fio, in an AMD SEV guest. This patch > resolves the failures. I think the right way to fix this is to just do a proper unwind insted of calling a catchall function. Can you try this patch? diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c index 25456d02eddb8c..47d7075053b6b2 100644 --- a/drivers/nvme/host/pci.c +++ b/drivers/nvme/host/pci.c @@ -842,7 +842,7 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req, sg_init_table(iod->sg, blk_rq_nr_phys_segments(req)); iod->nents = blk_rq_map_sg(req->q, req, iod->sg); if (!iod->nents) - goto out; + goto out_free_sg; if (is_pci_p2pdma_page(sg_page(iod->sg))) nr_mapped = pci_p2pdma_map_sg_attrs(dev->dev, iod->sg, @@ -851,16 +851,25 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req, nr_mapped = dma_map_sg_attrs(dev->dev, iod->sg, iod->nents, rq_dma_dir(req), DMA_ATTR_NO_WARN); if (!nr_mapped) - goto out; + goto out_free_sg; iod->use_sgl = nvme_pci_use_sgls(dev, req); if (iod->use_sgl) ret = nvme_pci_setup_sgls(dev, req, &cmnd->rw, nr_mapped); else ret = nvme_pci_setup_prps(dev, req, &cmnd->rw); -out: if (ret != BLK_STS_OK) - nvme_unmap_data(dev, req); + goto out_dma_unmap; + return BLK_STS_OK; + +out_dma_unmap: + if (is_pci_p2pdma_page(sg_page(iod->sg))) + pci_p2pdma_unmap_sg(dev->dev, iod->sg, iod->nents, + rq_dma_dir(req)); + else + dma_unmap_sg(dev->dev, iod->sg, iod->nents, rq_dma_dir(req)); +out_free_sg: + mempool_free(iod->sg, dev->iod_mempool); return ret; }